Eliminate std::vector from Type

[lattner]

Bugzilla Link	1209
Resolution	FIXED
Resolved on	Feb 22, 2010 12:53
Version	trunk
OS	All

Extended Description

Type::ContainedTys is a vector of PATypeHandle's. It would be much more efficient to coallocate the array
on the end of the type object. This is a little tricky due to the fact that Type has subclasses.

[llvmbot]

I would like to do this, Chris, but I'm not sure what you mean by "coallocate
the array on the end of the type object". Are you suggesting that we make
members like:

uint16_t NumContainedTys;
PATypeHandle* ContainedTys[];

in the Type class and then allocate additional space at the end of the object
for the pointers to the contained types? This would get rid of the std::vector.

If that's not what you mean, could you clarify, please?

[lattner]

I would like to do the standard trick of using:

struct foo {
stuff
T array[];
}

instead of:

struct foo {
stuff
T *array; // separate allocation.
}

In this case, T is PATypeHandle. Is that what you wanted to know?

-Chris

[llvmbot]

I think we're proposing the same thing, except:

1. Don't we need to keep the size of the array-at-the-end somewhere?
2. I added a PATypeHolder* in the Type class so it could access it regardless of
   the subclass. The subclass would be responsible for setting it to the correct
   address (inside the instantiated object).

Does this make sense or do you have something more clever in mind?

[lattner]

Yup, that sounds right!

-Chris

[llvmbot]

Candidate patch to implement this feature.

[llvmbot]

Implemented with these patches:

http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070402/046866.html
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20070402/046865.html